1. Technical Field
The present invention relates to a digital-to-analog converter for converting a digital signal into an analog signal.
2. Description of the Related Art
A digital-to-analog converter (DAC) is needed to process a product through a digital internal processing technique to produce an analog signal for communication, sound and the like. The DAC is a device for converting a coded digital signal into an analog signal.
The DAC has code dependent transient. The code dependent transient refers to a phenomenon that occurs when an output value differs from an input value according to each input code as the input value passes through the DAC. This is because an output value of the DAC for one input code affects an output value of the DAC for the next input code. The code dependent transient increases a harmonic component of the output value, thereby adversely affecting performance of the DAC. The harmonic component is measured based on spurious free dynamic range (SFDR), which indicates a difference between the signal strength of an output frequency f and the signal strength of frequency 2f of the harmonic component. If the SFDR is high, this may mean that the harmonic component is small and performance of the DAC is high.
As a method to attenuate the code dependent transient, a return to zero (RZ) technique is used. The RZ is a technique of forcibly converting half the input value to the DAC into 0 to prevent one input code from affecting the next input code (hereinafter, referred to as an input value).
However, since the RZ sets a section corresponding to half the input value to 0, it produces signal loss of about 6 dB in the output value. That is, in the RZ section, the input value is 0 and is thus not used. Accordingly, the output value correspondingly decreases. This results in waste of usable resources and requires separate amplification of the output value to compensate loss of the output value.